The following questions were posed by a reader of this previous blog post on flax seed nutrient absorption.

Hi Reed-
Thank you for answering my question. I have been a vegan for six years and have a degree in analytical chemistry. I read your 2007 article carefully several times. Do you feel that attempting to optimize the la to ala ratio is a valid measure?

Since vegan diets contain little or no DHA or EPA, people on vegan diets get these fatty acids by making them from alpha-linolenic acid. The rate of production of EPA and DHA from alpha-linolenic acid is very low. The reader’s question is whether or not changing the ratio of linoleic acid (LA) to alpha-linolenic acid (ALA) will result in a higher production of EPA and DHA. The same enzyme acts on both LA and ALA, so the thinking behind adjusting their ratio is that if there is less LA and more ALA for the enzyme to deal with, more ALA might be converted to DHA and EPA. Studies where the ratio of LA:ALA has been adjusted have had inconsistent results. There does not seem to be any disadvantage, however, to striving for a lower ratio of LA:ALA and a lower ratio might result in more EPA and DHA production. Some experts recommend a ratio of 2:1 to 4:1 for vegetarians. Several dietary changes can help to achieve a lower LA:ALA ratio:

• Use cooking oils that are rich in monounsaturated fats. Monounsaturated fats by themselves do not affect the LA:ALA ratio and, if substituted for oils high in LA, will result in a lower ratio. Oils that are high in monounsaturated fats include olive oil, canola oil, high-oleic sunflower oil, and high oleic-safflower oil.
• Consume adequate amounts of ALA. See http://www.vrg.org/journal/vj2007issue1/vj2007issue1.pdf for information on food sources of ALA.
• Avoid using cooking oils high in LA as your main cooking oil. Cooking oils that are high in LA include safflower oil, grapeseed oil, sunflower oil, corn oil, cottonseed oil, and soybean oil.

Do you recommend taking a dha supplement?

Vegan DHA supplements derived from DHA from microalgae have been shown to raise blood levels of DHA and EPA. We don’t know whether or not higher blood DHA and EPA levels will offer additional protection to vegetarians since they already have a low risk of heart disease. Higher blood levels of these fatty acids appear to reduce the risk of death from heart disease. The question of whether or not to take a DHA supplement should be an individual decision based on risk factors and family history.

Are nutrients also difficult to obtain from whole chia and sesame seeds?

I am not certain about whole chia seeds although I suspect that the same concerns that are seen with flax seeds would be present for whole chia seeds (not well digested). Hulled sesame seeds appear to be a better source of calcium than unhulled sesame seeds. The calcium in the hull of the sesame seed is in the form of calcium oxalate which is poorly absorbed. You can read more about this at
http://www.vrg.org/journal/vj96jul/vj967hot.htm.